A conventional fuel cell system, for example as disclosed in Patent Document 1, collects hydrogen contained in fuel exhaust gas exhausted from a fuel cell and combusts the collected hydrogen. The conventional fuel cell system collects water from combustion exhaust gas exhausted by the combustion, and removes ions from the collected water by means of an ion removal device. The conventional fuel cell system generates hydrogen that is used for power generation of the fuel cell through use of the deionized water from which ions have been removed.
FIG. 7 is a constitutional view showing the conventional fuel cell system described in Patent Document 1. As shown in FIG. 7, fuel cell system 70 is made up of fuel cell 71, fuel gas generator 72, gas-liquid separator 74, heat exchanger 75, degasifier 76, condensed water tank 78, ion removal device 79, and pure water tank 77.
Fuel gas generator 72 generates fuel gas to be supplied to fuel cell 71. Gas-liquid separator 74 condenses moisture contained in fuel exhaust gas exhausted from fuel cell 71, and separates the moisture into fuel exhaust gas condensed water and combustion gas containing hydrogen. Combustion section 73 of fuel gas generator 72 combusts the combustion gas containing hydrogen separated by gas-liquid separator 74. Heat exchanger 75 performs heat exchange to condense combustion exhaust gas exhausted by the combustion in combustion section 73, and generates combustion exhaust gas condensed water.
Degasifier 76 performs degassing treatment on the combustion exhaust gas condensed water condensed in heat exchanger 75 by means of exhaust air exhausted from fuel cell 71. Condensed water tank 78 stores the fuel exhaust gas condensed water condensed in gas-liquid separator 74, and the combustion exhaust gas condensed water degassed by degasifier 76 after condensed in heat exchanger 75. Ion removal device 79 removes ions contained in the condensed water stored in condensed water tank 78. Deionized water from which ions have been removed is stored into pure water tank 77.
However, in the conventional fuel cell system, the fuel exhaust gas condensed water condensed in gas-liquid separator 74 contains a large amount of carbon dioxide gas. The carbon dioxide gas is dissociated as bicarbonate ions in condensed water tank 78. For this reason, the condensed water stored in condensed water tank 78 contains a large amount of bicarbonate ions. This results in an increase in amount of ions to be removed in ion removal device 79. There has thus been a problem in that the durability of ion removal device 79 deteriorates to destabilize the operation of the fuel cell system in a short period of time. Patent Document 1: Unexamined Japanese Patent Publication No. 2005-129334